Welcome to the Community. It's essential you're able to export your files with ease. I'll be happy to give you a hand with this so you can enjoy the amazing features offered in QuickBooks without any hassle.
Based on what you've described, I suggest using a shorter date range just in case the report file you were previously exporting is too large. You can choose a date range by clicking the drop-down under Pre-selected date ranges. I also encourage you to check out this article that shows you how to: Export Data out of QuickBooks Online.
Let me know if this info helps. I'll be here in case you have other questions.